Which protocol is associated with ports 20 and 21?

The correct association of ports 20 and 21 with a specific protocol is FTP, which stands for File Transfer Protocol. FTP is a standard network protocol used to transfer files between a client and a server over a Transmission Control Protocol (TCP) connection.

Port 21 is typically used for the control connection, which is responsible for sending commands and responses between the FTP client and server. Port 20 is designated for the data connection, which is utilized when files are being transferred. This division allows for separate management of commands and the actual file transfer process, enhancing the efficiency of the protocol.

Understanding this port assignment is crucial for network configuration and troubleshooting, as it assists in determining which services are operating on which ports, ensuring the proper functioning of file transfer operations within networking environments.